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Old 02-12-2001   #1
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heads, cam, cats, and chip

Hello all,

I am the proud caretaker of a 1990 white 5.7L GTA (supposedly rare) and, I WANNA GO FASTER! Seriously, Here are the mods i've done so far: 3.42s in the rear, ground down the plenum EGR humps, laced MSD 8.8 wires, installed an adj FPR (set at 50 psi), bolted on an air foil, and opened up the air cleaner box. I run a consistent 15.4 (best of 15.25) in SLC, Utah at 4330 ft above sea level. My best 60 ft time is 1.97 (typically in the 2.20 range).

These are the mods i'm looking into: (just bought a house, don't have any money)

* a set of L98 'vette heads (ported, gasket matched, and
polished)
* Some sort of upgraded cam (as i've realized the factory
one suckes).
* Punching out the Cats (will this help. or is it just
stupid?).
* Going with 3.73s in the rear

What are your thoughts on these mods, and what could I expect form them? Maybe a diferent direction? If you have any other sugestions, please feel free to enlighten me, 'cause it's all about goin' faster! JD
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Old 02-12-2001   #2
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engine

Here are some ideas based on what I run.
3.70:1 gears. Trick flow 23 degree heads. Comp Cams roller 220/230 @.050 w/ .510" valve lift. Crane Gold Roller rockers, thin style to clear center bolt valve covers. SLP intake runners. Edelbrock header system w/ Dynomax catback exhaust. Ford Motorsport 30lb. injectors. B&M 2400 rpm holeshot converter.
Crane HI-6S ingition kit w/ Accel performance ignition module. Fastchip custom made PROM. Keep in mind that if you go with these mods and upgrade your injectors and cam to these extremes, you ABSOLUTELY HAVE to have a custom chip made for you. Fastchip custom prom run $350, but they will alter the settings on it at no extra charge after the initial programming if the car doesn't fun perfect for you. Hypertech chips are for stock injectors and cams rated up to 208degrees duration at .050. The setup I just gave you is good for about at least 350 horsepower and it pulls pretty good up to about 5800 rpm. Really hard to get any more upper rpm power out of it without supercharging because of the long intake runners. The ignition and exhaust upgrade itself really helped out. I performed those prior to all the other upgrades. The hallowed cat really did not buy me much. I also only run 40 psi of fuel pressure. For these motors, you shouldn't need more than that. With a good set of rubber out back, should not be any problem getting down into the low 13's. Good luck.
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Old 02-13-2001   #3
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Going faster

Congratulations on the home purchase. I understand your comment on the cash flow situation. Cams,headers and the like cost money. Wouldn't it be nice to have unlimited funds...... just dreaming. Why not try some simple things that might shave off a tenth or two. It seems like you have done everything with the stock induction system with the exception of a K&N air cleaner,about $30 from Summit. Synthetic motor and transmission oils, less than a $100 for both. Aluminum drive shaft less weight and faster response, saw one recently for $155. These mods might help you along as you are trying to recover from the home purchase. When funds allow, break open the engine. Just my .02.

Can you tell me about the gains you got with the adjustable fuel regulator? I have read some articles indicating that this change is significant.

I probaly would not hollow out the cats. There seems to be a lot of debate if this does any good. Something about hollow cats producing pressure waves in the exhaust.

Good luck
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Old 02-13-2001   #4
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Re: Going faster

Thanks for the replys. I already use a K&N filter, synthetic fluids only, and the car already has an aluminum driveshaft (I thought they all came with them, or was it an option?). Unfortunately I can't come up with that kind of cash right now for the mods silverado73 mentioned, but I do have a couple more questions. I read in a chevy high-po mag that porting the cast iron heads were worth almost as much as the factory vette ones. Any insight on this? Do you know of any other heads that would work on the L98 for for a low cost upgrade? I'd love to get my hands on a set of Trick flows, but it's not going to happen this year. Also, for this kind of set-up what is the most cam I can stuff in there with a performance resource chip? My plan of attack is this:


*3.73s in the rear
*Good cam (what about a non-roller set up?)
*aftermarket headers (don't know what kind yet)
*port, polish, & gasket match the factory heads, intake,
and plenum (Myself)
*I've herd about using an ultra-thin head gasket to boost compression (Any problems I might encounter with this?)
*milling the heads slightly to boost compression (Again, problems?)
*A good set of aftermarket runners (I'm leaning toward the SLP's but I herd you can't do much in the way of modifying them)
*Some sort of shift kit

Does any one have reccomendations on the above?

The car currently runs consistent 15.40s with a best of 15.25 (race gas and it was cool that day) and 60 ft times of 2.02 (best of 1.97) all at 4330 ft above sea level (SLC, Utah).

For JCyoung, I've done extensive research on the fuel presure regulator and all my other mods, and after installing it, I noticed a little extra punch. The references I used recommend 46 psi for the street and 50 psi for the track. I have always run 50, but it's all about the individual car and test n' tune. The regulator won't put you in the 13's but incremental changes like the ones I spoke of really add up. What mods have you completed so far?

Again thanks,
JD

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Old 02-14-2001   #5
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Going faster

JDs thanks for the info on the fuel regulator. As for your aluminum drive shaft, I am 95% sure that this was an option, code number JG1, if my memory serves. Frankie Rider, the web master would know for sure.

Concerning my modifications, not much at the moment due to confusion. My 87 GTA has 9330 original miles, no kidding. It still has the factory original Goodyear 245/50/16/VR rated tires. The car was owned by a collector for the first 10 years of its life and was sold to a friend with less than 3000 on the clock. He sold it to me 19 months ago. The car needed new valve seals due to dry rotting. The car is 100% stock and I am concerned that any modifications would move it out of the stock classification if I decided to show it. I read a horror story of what happened to Frankie Rider when one of his cars was moved out of the stock category because of chromed vales caps on his wheels. Ouch!!!!! talk about nit picking. My mods have been limited to the invisible. Synthetic fluids, K&N cleaner, removed MAF screens, and an air foil are all that I have done to date. I was thinking about a cat back, but once again would be fearful of having the classification changed. Any help on this topic would be appreciated. Thanks.
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Old 02-14-2001   #6
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parts

The motors take a lot of parts to really make a significant difference in performance. Trick flow heads are really not too expensive. About $850 for the aluminum set. I wouldn't do too much milling in hopes of getting compression up there. Milling and a thinner head gasket won't buy you more than half a point of compression. These motors run well with a little lower compression so you can get more total advance out of the ignition. As far as cams go, if you go with standard hydraulic, keep the advanced duration below 260 total degrees and about 210 degrees at .050. You can still run this cam with an aftermarket chip and 160 degree thermostat. If you do decide to mill the heads, keep the valve lift down to about .450" to .480" to be safe. Always check your valve to piston clearance though. For shift kits, I would personally recommend TransGo. I have had very good luck with their kits and the shift kits usually run about $65. Before I did any major mods to the car, I installed a Crane HI-6S ignition kit and an Accel distributor performance module and 8.5mm wires with new stock AC Delco plugs. With 120k on the car and motor, it ran 15.02 in 1/4 at 96mph. This is with no K&N, pressure regulator or even high test gas. Just make sure the car is tuned-up properly and the timing is correct and see what happens.
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Old 02-15-2001   #7
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Re: Going faster

Jc,
There are quite a few go fast mods you can make. Here are some suggestions:

* Port, polish, and gasket match the plenum, runners, intake, and heads. Also go with a threee angle valve job while you're at it. (I can tell you where to find references w/ pics for this if you are interested)

* Use an adj. FPR if you can get away with it (they have an adj. screw sticking out of the top)

* 3.42 or 3.73 gears (Big help off the line)

* upgrade your cam!

* Install a TransGo shift kit like Silverado73 suggested. I'll get one of these myself.

* An aftermarket chip (www.performanceresource.com offers
a chip that was tested to drop the ETs by almost 4/10s!
I'm installing this one in a couple weeks)

Those are off the top of my head. For some outstanding deald on performance parts, go to www.thirdgen.org classified section. I haven't bought any parts there yet, but I just found out about it the other day. The best test bed is somone who has already tried it. Individuals like Silverado73 and frank Rider are worth thier weight in gold, so I send out my greatest thanks to these guys along with every one else posting on sites like these.

Keep the Rubber side down,
JD
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Old 03-04-2001   #8
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Re: Going faster

Silverado,
I just received the TPIS insider secrets handbook. Concerning fuel pressure, they recommend 47 to 50 psi to better atomize fuel leaving the injector. Also, they stated the factory 350 injectors are good for at least 450 ponies. Any insight on this? I have to tell you, I was a little disappointed in TPIS' handbook. they really didn't tell me much more than I already knew, especialy for $25. Oh well, live and learn. I have decided to go with a roller cam, but can't settle on the grind. I'm just going to clean up the factory heads, intake and plenum, then go with the SLP runners. Can anyone give me a well founded cam profile that'll work on this daily driver, yet yeild maximum horsepower. Also, in completing these mods, will the speed density system require a custom chip?

Thanks in advance,
JD
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Old 03-04-2001   #9
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cam

You should run more than 40 psi of fuel pressure. Anything less usually does lead to improper atomization. You are correct. Stock injectors are rated at 22-24lbs. This is only good for upto about 350-375 horsepower!! You DO NOT want to run these motors lean on the top end. An easy way to check is to tap into the O2 sensor wire with a voltmeter. Wide open should yield about .7-.75 volts. If you are running around .5v, the motor is too lean and you need to upgrade to 30lb injectors. If you do this though, you need to have a custom chip made to take these injectors into account. If you go with a cam larger than 210 degrees duration @.050, you need to have a custom chip made also. Fastchip can do this for $350 and they will reprogram it anytime to adjust mixture settings or anything like it. Their chips take into account any head or exhaust upgrades, cam and injector upgrades, intake runner upgrades and gear or stall converter upgrades. If you make any of these upgrades using a standard aftermarket chip, like Hypertech, their chip's don't take any of these changes into account. For your cam, if you are not going to run a custom chip, keep it below 210 degrees duration @.050. I run a Comp Cams roller cam and they come made with 4 degrees of advance built in. I would recommend pn. 08-304-8. Specs are 210/220 degrees @.050 and valve lift is .500/.510". Your stock hydraulic roller lifters will work just fine, but I would recommend new performance valve springs and pushrods. They are cheap and could save your motor. Check out their website and ask for a free catalog from them. Hope this helps.

Chris
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